Despite the importance of a fully functional ankle joint for movement and balance, there are instances in which the pain that can be generated by certain pathologies justify fusion in order to alleviate on-going pain. It is sometimes necessary or desirable to cause fusion or arthrodesis of the primary bones that form the ankle joint, for example, in the case of osteoarthritis, post-traumatic osteoarthritis, ankle arthritis or after failure of total ankle replacement. In this instance given the role of the ankle in allowing for balance and movement, given the high loads to which the ankle joint is subjected, and given the relative lack of soft tissue to cover an implant, it is particularly important that the procedure result in a highly precise placement of the implant and fasteners, as well as a precise and secure joint immobilization.
Prior art devices for use in arthrodesis include wires, screws, plates and intramedullary devices. While such devices exist, each is lacking in providing one or more of the desired precision, stability, fixation, or relative ease of implantation that an orthopedic surgeon desires for such a device.
Thus, it is an object of the present invention is to provide an ankle fusion system and surgical method for implanting an implant in a human ankle, which allows for fusion of the distal end of a tibia, the talus and calcaneus (i.e. the “T-T-C” interface) using a lateral incision to the tibia, talus, fibula and calcaneus region, removing some or all of a fibula in the incision area, attaching the implant to the tibia, talus and calcaneus in a generally central area of the lateral ankle so as to encourage the bones to fuse together. The system includes a lateral plate having a central rail member with fastener holes and preferably including one or more locking holes and/or compression holes. The rail member is planar across its width and includes a slight undulation in the z dimension along the longitudinal axis to accommodate a generalized surface of the distal tibia in the place of the fibula that has been removed. The inferior portion of the plate forms a C-shaped stirrup under the calcaneus and includes at its inferior-most end a screw hole for the placement of a fusion screw, which is advantageously a compression screw of sufficient length to extend through the T-T-C interfaces. The invention further includes a jig, which attaches to the rail to permit a placement of the T-T-C screw that avoids impingement with the other plate fasteners, and also that is at the optimal angle to achieve fusion. The fusion is augmented by the use of the separate (i.e. which does not cooperate directly with the plate) fusion screw that angles up through the calcaneus, talus to the anterior portion of the distal tibia.
Apart from the calcaneal stirrup segment, the rail member has a first lateral segment that abuts the calcaneus, a second lateral segment that abuts the talus, and a third lateral segment that abuts the tibia. The rail member further includes tabs or wing portions on each of the calcaneal segment, the talar segment, and the tibial segment. The calcaneal wing includes a plurality of fastener holes, i.e., preferably a triangular arrangement of three, and a slot for placement wires, such as k-wires, while a tab extends from the anterior edge of the rail member in the talar segment substantially in opposition to a slightly posterior talar tab, each of which has a single locking screw hole. The anterior talar wing also has a slot for a guide wire. The tibial segment has stepped tabs, which wrap around the tibia on each of the anterior and posterior sides with each tab including a single locking screw hole. This segment also includes compression slots below and above the stepped tabs. The talar segment of the plate also includes a central locking hole that can be used for a screw as well as to position and fasten the targeting jig relative to the plate.
The calcaneal jig in accordance with the present invention has a large C-shaped end, which can be pivoted in relation to the central talar hole, and having a drill guide to position a second fusion screw in a posterior portion of the calcaneus. Examples of the conditions for which the present invention are useful include arthritis with or without associated deformity of the ankle and subtalar joint, rheumatologic arthritis and deformity, severe ankle and subtalar arthrosis, talar collapse, avascular necrosis of the talus, hindfoot deformity, stage 4 flatfoot and/or Charcot neuroarthropathy and/or deformity. The invention can be used for both a tibiotalocalcaneal and a tibiocalcaneal (TC) arthrodesis where a partial or total talectomy is necessary.